SINGAPORE, March 27 (Reuters) - Cathay Pacific Airways Ltd on Wednesday said it would no longer allow its unionized pilots to refuse training roles despite a near four-year union ban in a move that a pilot said could raise workplace tensions.

Relations between Cathay and its 3,000-plus pilots have become strained as the airline seeks to cut costs as part of a three-year transformation plan designed to make it more competitive against Chinese and Middle Eastern rivals and low-cost carriers.

The union ban on pilot training has made it more difficult for the airline to promote pilots quickly when it has been expanding capacity and also when a global pilot shortage prompted some expat pilots to take other jobs.

A Cathay spokesman said the ban had been in place since 2015.

"The selection and appointment of training captains will be solely at the company's discretion," the Cathay spokesman said of the new policy on Wednesday. "This means, suitable pilots no longer have the right to refuse a training appointment."

A Cathay pilot, speaking on condition of anonymity, told Reuters these roles attracted extra pay and some captains had quit the union to take them up during the ban. But the pilot also said the company's action was not likely to be received well by the workforce.

The Cathay spokesman said the airline's trainers had faced undeserved criticism during the ban for supporting the company's training programs which enable more junior pilots to progress.

The Hong Kong Aircrew Officer Association (HKAOA) said on Wednesday evening that it could not comment immediately.

In January, the HKAOA members overhwelmingly voted down a contract proposal which offered at least a 1 percent pay rise and some housing guarantees even though it had been recommended by the union's leadership.

The announcement to pilots on the ban was made shortly after Cathay agreed to buy low-cost carrier Hong Kong Express Airways Ltd from cash-strapped Chinese conglomerate HNA Group for HK$4.93 billion ($628 million), giving it a foothold in the fast-growing budget travel market. (Reporting by Jamie Freed. Editing by Jane Merriman)